crtique my build please

My dad and I are upgrading to big block power in his 1-ton chevy trail/mud vehicle.  We are wanting gobs (relative) torque as early in the power band as possible and have drafted this build.  This is all on a 2-bolt 454 out of a '78 pickup and we are hoping for 400hp/500ft/lb of torque.  Can any of you critique the elements of our build and do two things?  1. Estimate the output numbers and 2. suggest alternative elements for better power?  Proposed engine specs are below.

Engine Summary
Goal: Bad ass stump puller
Engine Type: 1978 C-3500 454 built to a 460
Operating Range: 0-5000 RPM
HP/Torque: 400/500
Displacement: 460 Cubic Inch
Compression ratio: 8.7
Bore: 4.250” + 0.30” = 4.280”
Stroke: 4.00

Block
ID: GM 10T 861959 Hi Perf Pass
Production Year: 1978
Bore: 4.250” + 0.30” = 4.280”
Main Caps: Two-bolt

Cylinder Heads
Type: OEM 781
ID: 336781
Port Type: Oval
Combustion Chamber: 118 CC
Intake: 256 CC
Exhaust: 114 CC

Intake Manifold
Type: Edelbrock Performer
ID: 2161
Operating Range: 0-5500 RPM
Ports: Oval

Camshaft (Not sure about this cam...)
Type: Edelbrock Performer-Plus
ID: 2162
Operating Range: 1500-5500

Pistons
Type: Open to suggestions
ID:
Oversize: + 0.30
Stroke: 4.00
Compression: 8.7

Once again, any thoughts on the expected output numbers and critiques you may have are welcome.  Also, even though this is a budget build is there anything relatively affordable that I missed that would be worth it?  How would all of this hold up in a 2-bolt main?  Worth machining it to a 4-bolt?

Thanks again!  

Forgot to mention that we will likely be running hedman headers.  Also, another cam we are considering is CompCams Xtreme 4x4™, X4 254H  

The 781 heads are a good choice for bottom and mid range power. Take time and bowl blend the valve pockets, clean the short turn radius, gasket match and these heads really come to life. Do not be fooled by literature that claims these heads to have 118cc comb. chambers. They usually have at least 121cc's. Keep this in mind when you figure in the compression ratio. I used to run a Edelbrock Performer cam in one of my 454's and with a 9.5:1 comp ratio, it made incredible torque and peaked out at 5300 rpm. I have a Comp Extreme 4x4 254H in my crew cab dually with 10:1 comp ratio and 781 heads with the mod's I talked about before and it's quite the monster! Check it out on youtube (A169KL) and see it in action. One piece I always use on a block that is not zero decked is the .020 steel shim head gasket. The block was designed to have this gasket in place and if you think about "quench" being perfect in the .038-.040 range, the .020 gasket is the only way to go. Dont let anyone tell you it's "old school" or they dont hold up. Chevy used them for years and never had problems and neither have I. If you use a composition head gasket, usually around .040 and a - .020 deck height, you now have .060 clearance and that's way to much for maximum power and effiency. I always run forged pistons in my builds with file fit rings but there is nothing wrong with a good hyperuetectic piston for a moderate build. If you file fit your rings on a hyper piston, the top gap must be filed wide, usually around .022. Are you useing stock 3/8 bolt rods? If you plan on getting new rod bolts and resizing, then consider a set of Eagle SIR rods. There much stronger and cost the same as fixing your old ones. Good luck on your build.  JW.  

Sweet!  Nice dually.  We were planning on using the stock bolts because we havent really thought about it.  Thank you very much for you thoughts and advice.  It will truly help us with this build.  

No problem. Good luck!  JW.  

I would just stroke it to a 496 with a cheap cast kit. some how a 496 like yours is cranking out 750hp! with your heads ported. But you'd probably be at 600 atleast with 600ftlbs of torque.  

you should get 500hp and 500ftlbs of torque though which should be enough to light up the tires